In a current Long-Term Evolution (LTE) system, a physical-layer data shared channel performs data transmission by taking Transmission Block (TB) as a basic unit. A receiver judges whether a current TB is correctly received or not through a Cyclic Redundancy Check (CRC) of the TB. If the TB is correctly received, the receiver feeds back an Acknowledgement (ACK) message to a sender. If the TB is not correctly received, the receiver feeds back a Negative Acknowledgement (NACK) message to the sender. The sender retransmits data to the receiver after receiving the NACK message, and retransmission is still performed by taking TB as the unit.
When a size of a TB exceeds a specified threshold, the sender is usually required to perform Code Block (CB) segmentation to segment the TB into multiple CBs, and operations of coding, rate matching, CB concatenation and the like are performed on each CB for sending to the receiver respectively.
A CRC is added to each CB before coding, and in addition, each TB also has a CRC. In LTE, lengths of the two CRCs are both 24 bit. A CB CRC is configured for premature termination of decoding. The CB CRC may also check correctness of a CB. If the CB CRC succeeds in checking, it is indicated that the CB is a correct CB, and if the CB CRC fails in checking, it is indicated that the CB is an incorrect CB.
The TB CRC is configured for correctness checking of a received TB. When the TB CRC fails in checking at the receiver, it is indicated that the TB is incorrectly received, and the TB is required to be retransmission. When a TB includes a relatively larger number of CBs, relatively more resources are occupied by retransmission. For example, as shown in FIG. 1, a TB includes 8 CBs, and only CB2 and CB5 are incorrectly decoded during first transmission. However, during retransmission, the other CBs without errors are also required to be retransmission. This is because an ACK/NACK of the current LTE system is fed back on the basis of a TB, there is no CB-based ACK/NACK feedback and CB-based feedback may cause extremely high uplink ACK/NACK feedback overhead.
Packet coding is a technology for coding between data packets, i.e. a process of coding multiple source data packets to generate check data packets. As shown in FIG. 2, a process of generating a check sequence at a corresponding position in a check data packet from an information sequence at a corresponding position in a source data packet is packet coding. Each check data packet includes data at corresponding positions in one or more check sequences. There may be various packet coding methods. For example, check data packets may be generated in a manner of performing an exclusive OR operation on each source data packet, the check data packets may also be generated in a Reed-Solomon coding manner, and the check data packets may further be generated in a fountain code or network coding manner.
In a digital mobile communication system, a coding bit sequence obtained by rate matching is required to be modulated into digital baseband signal(s) for transmission. In an LTE system, common modulation constellation diagrams include Binary Phase Shift Keying (BPSK), Quadrature Phase Shift Keying (QPSK), 16 Quadrature Amplitude Modulation (16QAM), 64 Quadrature Amplitude Modulation (64QAM) and the like. All of these modulation constellation diagrams include one or more limited discrete constellation points configured to represent amplitudes and phases of digital baseband signals, and geographical distances between the constellation points are called as Euclidean distances. If Euclidean distances between adjacent constellation points are equal and each constellation point is uniformly distributed in a constellation diagram, the modulation constellation diagram is called as a uniform constellation diagram. For example, the modulation constellation diagrams such as QPSK, 16QAM and 64QAM adopted in the LTE system are all uniform constellation diagrams. On the contrary, if Euclidean distances between adjacent constellation points are unequal or each constellation point is non-uniformly distributed in a constellation diagram, the constellation diagram is called as a non-uniform constellation diagram.
In a related technology, data retransmission of a physical layer is based on the whole TB, that is, if at least one CB in TB signal(s) is incorrectly received during first transmission, the whole TB is required to be retransmission during retransmission and CBs which are correctly received during first transmission are still required to be transmitted during retransmission, which is obviously unfavorable for utilization of a spectrum resource during retransmission. For improving retransmission efficiency, an apparent method is that a receiver performs feedback on each CB and then a sender may only be required to retransmit an incorrectly received CB. However, the method has an obvious defect that overhead of feedback signaling is increased, and an ACK or NACK is fed back for each CB, which may increase the amount of feedback signaling by multiple times and even dozens of times to severely exceed a bearing capability of a feedback channel. Therefore, the method is not adopted by a mainstream communication technology such as LTE.